Surface coating agents

ABSTRACT

Compounds useful as surface coating agents, including compounds of the formula:  
                 
 
     wherein X 1  comprises a first photoreactive species; X 2  comprises a second photoreactive species; Y comprises a nonpolymeric core molecule comprising an aromatic group; and Z comprises at least one charged group. The Y core can include an aromatic group such as a benzene radical, the charged groups Z can be independently selected from the organic acids that include sulfonic acid, carboxylic acid, and phosphoric acid, and the photoreactive species of X 1  and X 2  can independently be aryl ketones, such as those selected from the group acetophenone, benzophenone, anthraquinone, anthrone, and anthrone-like heterocycles, and their substituted derivatives. Examples of such coating agents include 4,5-bis(4-benzoylphenylmethyleneoxy) benzene-1,3-disulfonic acid di(potassium and/or sodium) salt, 2,5-bis(4-benzoylphenylmethyleneoxy) benzene-1,4-disulfonic acid di(potassium and/or sodium) salt (Compound II), and 2,5-bis(4-benzoylphenylmethyleneoxy) benzene-1-sulfonic acid monopotassium and/or monosodium salt.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] The present application is a continuation of U.S. patentapplication Ser. No. filed Jun. 25, 2001 and assigned Ser. No.09/888,709, which is a continuation of U.S. patent application filedDec. 14, 1999 and assigned Ser. No. 09/460,551, the entire disclosure ofwhich is incorporated herein by reference.

TECHNICAL FIELD

[0002] The present invention relates to chemical compounds providingboth charged groups as well as photoreactive species. In a relatedaspect, the invention relates to chemical compounds for use as surfacecoating agents.

BACKGROUND OF THE INVENTION

[0003] The chemical modification of surfaces to achieve desired chemicaland/or physical characteristics has been previously described. Forexample, U.S. Pat. Nos. 4,722,906; 4,973,493; 4,979,959; 5,002,582; and5,512,329 (each of which is commonly owned by the assignee of theinvention described herein, and the disclosure of each is incorporatedherein by reference), relate to surface modification by the use oflatent reactive groups to achieve covalent coupling of reagents such asbiomolecules and synthetic polymers to various substrates. The preferredlatent reactive group is typically described as a photochemicallyreactive functional group (“photoreactive species”). When exposed to anappropriate energy source, a photoreactive species undergoes atransformation from an inactive state (i.e., ground state) to a reactiveintermediate capable of forming covalent bonds with appropriatematerials.

[0004] Such latent reactive groups can be used, for instance, to firstderivative a target molecule (e.g., thermochemically), in order to thenphotochemically attach the derivatized target molecule to a surface.Such a sequential approach is suitable in many situations, but can lacksuch attributes as speed, versatility, and ease of use, particularlywhen used with target molecules that are inherently difficult to firstderivative or under conditions that would result in loss of biologicalactivity.

[0005] Latent reactive groups can also be used to preparephotoactivatable heterobifunctional molecules as linking agents, e.g.,having a photoreactive species at one end or portion with athermochemical attachment group at another (see, e.g., theabove-captioned '582 patent, and U.S. Pat. No. 4,309,453, Reiner etal.). Such linking agents can be used to either attach nonreactivecompounds to a surface or to prime a relatively inert surface in orderto render it reactive upon exposure to suitable actinic radiation.

[0006] U.S. Pat. No. 5,414,075 (commonly owned by the assignee of thepresent invention and incorporated by reference herein), describes theuse of linking agents to prime a surface to provide the surface withphotoactivatable groups. This patent describes a restrained,multifunctional reagent useful for priming a support surface, or forsimultaneous application with a target molecule to a support. Reagentssuch as those described above, including those described in the '075patent, are generally hydrophobic. As a result, they are of relativelylow solubility in aqueous systems, thereby often limiting theirusefulness in hydrophilic applications.

[0007] U.S. Pat. No. 5,714,360, also commonly owned by the presentassignee (and also incorporated herein by reference), describes achemical linking agent comprising a di-or higher functionalphotoactivatable charged compound. The linking agent provides at leastone group that is charged under the conditions of use, in order toprovide improved water solubility, and two or more photoactivatablegroups in order to allow the agent to be used as a linking agent inaqueous systems. The “Y group” that provides the core radical is definedas a radical containing one or more charged groups, such as the linearand heterocyclic nitrogen-containing (e.g., quaternary ammonium)radicals exemplified therein. In a preferred embodiment, the chargedgroups include, but are not limited to, salts of organic acids (such assulfonate, phosphonate, and carboxylate groups), onium compounds (suchas quaternary ammonium, sulfonium, and phosphonium groups), andprotonated amines, as well as combinations thereof. The photoreactivespecies can be provided by two or more radicals of an aryl ketone suchas benzophenone.

[0008] While the reagents of the art are sufficient, if not preferred,for many applications, there remain applications in which various otherproperties or attributes, such as water solubility, ease of synthesisand/or hemocompatability, are not optimally provided by the reagents ofthe art.

SUMMARY OF THE INVENTION

[0009] The present invention provides compounds useful as coatingagents. In one aspect, the present invention provides a compoundcomprising a nonpolymeric core molecule comprising an aromatic group,the core molecule having attached thereto, either directly orindirectly, one or more substituents comprising negatively chargedgroups, and two or more photoreactive species, wherein the photoreactivespecies are provided as independent photoreactive groups. The first andsecond photoreactive species of the present coating agent can,independently, be identical or different.

[0010] In a preferred embodiment the reagent comprises a compound of theformula:

[0011] wherein X₁ comprises a first photoreactive species;

[0012] X₂ comprises a second photoreactive species;

[0013] Y comprises a nonpolymeric core molecule comprising an aromaticgroup; and

[0014] Z comprises at least one charged group.

[0015] In such an embodiment, for instance, Y can include an aromaticgroup such as a benzene radical, the charged groups Z can beindependently selected from the salts of organic acids that includesulfonic acid, carboxylic acid, and phosphoric acid, and thephotoreactive species of X₁ and X₂ can independently be aryl ketones,such as those selected from the group acetophenone, benzophenone,anthraquinone, anthrone, and anthrone-like heterocycles, and theirsubstituted derivatives.

[0016] A coating agent of the invention has broad applicability,particularly since it can be used in surface modification reactionsystems where previous agents have not been effective or optimal. Inparticular, the presence of one or more charged groups (e.g., salts ofsulfonic, carboxylic and phosphoric acids) provides the agent withenhanced water solubility. This, in turn, allows the coating agent to beused in reaction systems favoring water soluble agents. A coating agentof the present invention thereby provides an improved combination ofsuch properties as coating density and structural stability, allowingthe agent to be used in a broad range of reaction systems.

[0017] Moreover, the presence of photoreactive species permits the agentto be used with a wide variety of support surfaces. The coating agentcan be used alone as a coating composition for a support surface, inorder to provide a surface primed with the coating agent itself. In thisembodiment, the coating agent provides the surface with desirableproperties of the coating agent itself, such as, for example,antithrombogenicity, lubricity, hemocomopatability,wettability/hydrophilicity, durability of attachment to the surface,biocompatability, and bacterial adhesion.

DETAILED DESCRIPTION

[0018] Compounds of this invention comprise a nonpolymeric core moleculecomprising an aromatic group, the core molecule having attached thereto,either directly or indirectly, one or more substituents comprisingnegatively charged groups, and two or more substituents comprisingphotoreactive species, wherein the photoreactive species are provided asindependent photoreactive groups.

[0019] In a preferred embodiment, the core is provided as the residue ofa polyhydroxy benzene starting material (e.g., formed as a derivative ofhydroquinone, catechol, or resorcinol), in which the hydroxy groups havebeen reacted to form an ether (or ether carbonyl) linkage to acorresponding plurality of photogroups.

[0020] In one embodiment, a coating agent of this invention furthercomprises one or more optional spacers that serve to attach a coremolecule to corresponding photoreactive species, the spacer beingselected from radicals with the general formula:

—O—(CH₂)_(n)—, and

—(C₂H₄O)_(m)—C₂H₄O—,

[0021] wherein n is a number greater or equal to 1 and less than about5, and m is a number greater or equal to 1 and less than about 4.

[0022] In a particularly preferred embodiment, such coating agents areselected from the group 4,5-bis(4-benzoylphenylmethyleneoxy)benzene-1,3-disulfonic acid di(potassium and/or sodium) salt,2,5-bis(4-benzoylphenylmethyleneoxy) benzene-1,4-disulfonic aciddi(potassium and/or sodium) salt, 2,5-bis(4-benzoylphenylmethyleneoxy)benzene-1-sulfonic acid monopotassium and/or monosodium salt. AgentFormula 4,5-bis(4-benzoyl- phenylmethyleneoxy) benzene-1,3-disulfonicdi(potassium and/or sodium) salt Compound I

2,5-bis(4-benzoyl- phenylmethyleneoxy) benzene-1,4-disulfonic aciddi(potassium and/or sodium) salt Compound II

2,5-bis(4-benzoyl methyleneoxy) benzene-1- sulfonic acid monopotassiumand/or monosodium salt Compound III

[0023] Suitable core molecules of the present invention includenonpolymeric radicals having a low molecular weight (e.g., 100-1000 MW).Suitable core molecules provide an improved combination of suchproperties as coating density, structural stability, ease ofmanufacture, and cost. Further, core molecules can be provided withwater soluble regions, biodegradable regions, hydrophobic regions, aswell as polymerizable regions. Examples of suitable core moleculesinclude cyclic hydrocarbons, such as benzene and derivatives thereof.

[0024] As used herein, a “charged” group generally refers to a groupthat is present in ionic form in solution, i.e., carries an electricalcharge under the conditions (e.g., pH) of use. The charged groups arepresent, in part, to provide the compound with desired water solubility.Additionally, such charged groups provide a combination of suchdesirable characteristics as antithrombogenicity and hemocompatability.

[0025] The type and number of charged groups in a preferred coatingagent are sufficient to provide the agent with a water solubility (atroom temperature and optimal pH) of at least about 0.1 mg/ml, andpreferably at least about 0.5 mg/ml, and more preferably at least about1 mg/ml. Given the nature of the surface coating process, coating agentsolubility levels of at least about 0.1 mg/ml are generally adequate forproviding useful coatings of target molecules (e.g., polymer layers) onsurfaces.

[0026] The coating agent of the present application can thus becontrasted with many coating agents in the art, which are typicallyconsidered to be insoluble in water (e.g., having a comparable watersolubility in the range of about 0.1 mg/ml or less, and more often about0.01 mg/ml or less). For this reason, conventional coating agents aretypically provided and used in solvent systems in which water is eitherabsent or is provided as a minor (e.g., less than about 50% by volume)component.

[0027] Examples of suitable charged groups include salts of organicacids (e.g., sulfonate, phosphonate, and carboxylate groups), as well ascombinations thereof. A preferred charged group for use in preparingcoating agents of the present invention is a sulfonic acid salt, e.g.,derivatives of SO₃ ⁻ in which the counterion is provided by the salts ofGroup I alkaline metals (Na, K, Li ions) to provide a suitablepositively charged species.

[0028] Photoreactive species are defined herein, and preferred speciesare sufficiently stable to be stored under conditions in which theyretain such properties. See, e.g., U.S. Pat. No. 5,002,582, thedisclosure of which is incorporated herein by reference. Latent reactivegroups can be chosen that are responsive to various portions of theelectromagnetic spectrum, with those responsive to ultraviolet andvisible portions of the spectrum (referred to herein as “photoreactive”)being particularly preferred.

[0029] Photoreactive species respond to specific applied externalstimuli to undergo active specie generation with resultant covalentbonding to an adjacent chemical structure, e.g., as provided by the sameor a different molecule. Photoreactive species are those groups of atomsin a molecule that retain their covalent bonds unchanged underconditions of storage but that, upon activation by an external energysource, form covalent bonds with other molecules.

[0030] The photoreactive species generate active species such as freeradicals and particularly nitrenes, carbenes, and excited states ofketones upon absorption of electromagnetic energy. Photoreactive speciescan be chosen to be responsive to various portions of theelectromagnetic spectrum, and photoreactive species that are responsiveto e.g., ultraviolet and visible portions of the spectrum, are preferredand can be referred to herein occasionally as “photochemical group” or“photogroup.”

[0031] The use of photoreactive species in the form of photoreactivearyl ketones are preferred, such as acetophenone, benzophenone,anthraquinone, anthrone, and anthrone-like heterocycles (i.e.,heterocyclic analogs of anthrone such as those having N, O, or S in the10-position), or their substituted (e.g., ring substituted) derivatives.Examples of preferred aryl ketones include heterocyclic derivatives ofanthrone, including acridone, xanthone, and thioxanthone, and their ringsubstituted derivatives. Particularly preferred are thioxanthone, andits derivatives, having excitation energies greater than about 360 nm.

[0032] The functional groups of such ketones are preferred since theyare readily capable of undergoing theactivation/inactivation/reactivation cycle described herein.Benzophenone is a particularly preferred photoreactive moiety, since itis capable of photochemical excitation with the initial formation of anexcited singlet state that undergoes intersystem crossing to the tripletstate. The excited triplet state can insert into carbon-hydrogen bondsby abstraction of a hydrogen atom (from a support surface, for example),thus creating a radical pair. Subsequent collapse of the radical pairleads to formation of a new carbon-carbon bond. If a reactive bond(e.g., carbon-hydrogen) is not available for bonding, the ultravioletlight-induced excitation of the benzophenone group is reversible and themolecule returns to ground state energy level upon removal of the energysource. Photoactivatible aryl ketones such as benzophenone andacetophenone are of particular importance inasmuch as these groups aresubject to multiple reactivation in water and hence provide increasedcoating efficiency.

[0033] The azides constitute a preferred class of photoreactive speciesand include derivatives based on arylazides (C₆R₅N₃) such as phenylazide and particularly 4-fluoro-3-nitrophenyl azide, acyl azides(—CO—N₃) such as benzoyl azide and p-methylbenzoyl azide, azido formates(—O—CO—N₃) such as ethyl azidoformate, phenyl azidoformate, sulfonylazides (—SO₂—N₃) such as benzenesulfonyl azide, and phosphoryl azides(RO)₂PON₃ such as diphenyl phosphoryl azide and diethyl phosphorylazide. Diazo compounds constitute another class of photoreactive speciesand include derivatives of diazoalkanes (—CHN₂) such as diazomethane anddiphenyldiazomethane, diazoketones (—CO—CHN₂) such as diazoacetophenoneand 1-trifluoromethyl-1-diazo-2-pentanone, diazoacetates (—O—CO—CHN₂)such as t-butyl diazoacetate and phenyl diazoacetate, andbeta-keto-alpha-diazoacetates (—CO—CN₂—CO—O—) such as t-butyl alphadiazoacetoacetate. Other photoreactive species include the diazirines(—CHN₂) such as 3-trifluoromethyl-3-phenyldiazirine, and ketenes(—CH═C═O) such as ketene and diphenylketene.

[0034] Upon activation of the photoreactive species, the coating agentsare covalently bound to each other and/or to the material surface bycovalent bonds through residues of the photoreactive species. Exemplaryphotoreactive species, and their residues upon activation, are shown asfollows (wherein R and R can be the same or different independentlyrepresent any non-interfering group). Photoreactive Group ResidueFunctionality aryl azides amine R—NH—R′ acyl azides amide R—CO—NH—R′azidoformates carbamate R—O—CO—NH—R′ sulfonyl azides sulfonamideR—SO₂—NH—R′ phosphoryl azides phosphoramide (RO)₂PO—NH—R′ diazoalkanesnew C—C bond diazoketones new C—C bond and ketone diazoacetates new C—Cbond and ester beta-keto-alpha- new C—C bond and diazoacetatesbeta-ketoester aliphatic azo new C—C bond diazirines new C—C bondketenes new C—C bond photoactivated new C—C bond ketones and alcohol

[0035] In one embodiment, the coating agent of the present inventionfurther includes optional spacers between the nonpolymeric aromatic coremolecule and one or more of the photoreactive species. A spacer isprovided in situations when it is desired to provide more distancebetween the photoreactive species and the core molecule. For example, itcan be desirable to provide a spacer to avoid steric hindrance that mayresult between the core molecule and the photoreactive species, thusinhibiting the photoreactive species from forming covalent bonds with asupport surface (in terms of the second photoreactive species), or fromserving as a linking agent for attaching natural and synthetic polymersto a surface.

[0036] The coating agent can be applied to the surface of interest inany suitable manner. For example, the coating agent can be applied bydip coating or by dispersing the agent on the surface (for example, byspray coating). Suitable methods of application include application insolution, dipping, spray coating, knife coating, and roller coating. Ina particularly preferred embodiment, the coating agent is applied to thesurface via spray coating, as this application method provides increaseddensity of the coating agent on the support surface, thereby improvingdurability.

[0037] The invention will be further described with reference to thefollowing non-limiting Examples. It will be apparent to those skilled inthe art that many changes can be made in the embodiments describedwithout departing from the scope of the present invention. Thus thescope of the present invention should not be limited to the embodimentsdescribed in this application, but only by embodiments described by thelanguage of the claims and the equivalents of those embodiments. Unlessotherwise indicated, all percentages are by weight.

EXAMPLES Example 1 Preparation of 4,5-bis(4-benzoylphenylmethyleneoxy)Benzene-1,3-disulfonic Acid Disodium Salt (Compound I)

[0038] 4,5-bis(4-benzoylphenylmethyleneoxy) benzene-1,3-disulfonic aciddisodium salt (Compound I) was prepared as follows. An amount (9.0 g,0.027 moles) of 4,5-dihydroxy 1,3-benzene disulfonic acid disodium saltmonohydrate was added to a 250 ml, 3 necked round bottom flask fittedwith an overhead stirrer, gas inlet port, and reflux condenser. Anamount (15 g, 0.054 moles) of 4-bromomethylbenzophenone (BMBP), 54 mltetrahydrofuran (THF), and 42 ml deionized water were then added. Theflask was heated with stirring under an argon atmosphere to reflux. Theargon atmosphere was maintained during the entire time of refluxing.

[0039] After reflux was reached, 9.0 ml (6 N, 0.054 moles) of a sodiumhydroxide solution was added through the reflux condenser. The reactionwas stirred under reflux for 3 hours. After this time, a second portionof BMBP, 3.76 g (0.014 moles), and 3.6 ml (6 N, 0.022 moles) of sodiumhydroxide were added. The reaction was continued under reflux for morethan 12 hours, after the second BMBP addition.

[0040] The reaction mixture was evaporated at 40° C. under vacuum on arotary evaporator to give 46 g of a yellow paste. The paste wasextracted by suspending three times in 50 ml of chloroform at 40° C. for30 minutes. A centrifuge was used to aid in the decanting of thechloroform from the solid. The solid was collected on a Buchner funnel,after the last extraction, and air dried for 30 minutes. The solid wasthen dried by using a rotary evaporator with a bath temperature of 50°C. at a pressure of about 1 mm for 30 minutes.

[0041] The dried solid, 26.8 g, was recrystallized from 67 ml of waterand 67 ml of methanol. The dried purified product amounted to 10.4 g(the theoretical yield was 19.0 g) with absorbance of 1.62 at 265 nm fora concentration of 0.036 mg/ml.

Example 2 Preparation of 2,5-bis(4-benzoylphenylmethylencoxy)Benzene-1,4-disulfonic Acid Dipotassium Salt (Compound II)

[0042] 2,5-bis(4-benzoylphenylmethyleneoxy) benzene-1,4-disulfonic aciddisodium salt (Compound II) was prepared as follows. An amount (15.0 g,0.043 moles) of 2,5-dihydroxy 1,4-benzene disulfonic acid dipotassiumsalt was added to a 500 ml, 3 necked round bottom flask fitted with anoverhead stirrer, gas inlet port, and reflux condenser. An amount (23.75g, 0.086 moles) of BMBP, 10.0 g (0.094 moles) of sodium carbonate, 90 mlof methanol, and 90 ml deionized water were then added. The flask washeated with stirring under an argon atmosphere to reflux. The argonatmosphere was maintained during the entire time of refluxing. Thereaction was stirred under reflux for 2 hours.

[0043] A second portion of BMBP, 6.25 g (0.023 moles), and 2.65 g (0.025moles) sodium carbonate were added. The reaction was continued underreflux for 2 more hours, after the second BMBP addition.

[0044] The reaction mixture was filtered and dried to give 43.6 g of asemi-dry solid. The solid was dried to give 26.8 g of a gray powder (thetheoretical yield was 31 g).

Example 3 Preparation of 2,5-bis(4-benzoylphenylmethyleneoxy)Benzenesulfonic Acid Sodium and/or Potassium Salt (Compound III)

[0045] 2,5-bis(4-benzoylphenylmethyleneoxy) benzenesulfonic acidmonosodium and/or monopotassium salt was prepared as follows. An amount(1.98 g, 0.0087 moles) of 2,5-dihydroxybenzene sulfonic acid potassiumsalt was added to a 100 ml, 3 necked round bottom flask fitted with anoverhead stirrer, gas inlet port, and reflux condenser. An amount (4.75g, 0.017 moles) of BMBP; 2.9 ml (0.017 moles) of 6N sodium hydroxide; 18ml of methanol; and 14 ml of deionized water were then added. The flaskwas heated with stirring under an argon atmosphere to reflux. The argonatmosphere was maintained during the entire time of refluxing. Thereaction was stirred under reflux for 1 hour.

[0046] A second portion of BMBP, 1.25 g (0.0045 moles), and 1.1 ml(0.0066 moles) of 6N sodium hydroxide were added. The reaction wascontinued under reflux for 1 more hour, after the second BMBP addition.

[0047] At the end of the reaction there were two liquid layers present.The reaction mixture had solidified 2 days later; the solid was filteredand dried to give 5.95 g of a light tan solid (the theoretical yield was5.1 to 5.3 g).

Example 4 Compound I Coating on Hydrogel Matrix

[0048] An experiment was performed to demonstrate the effectiveness ofusing Compound I as a coating agent on a polyvinylpyrrolidone (PVP)based, lubricious, hydrogel matrix.

[0049] The concentrations for the formulations came out of design ofexperiments performed with Compound I/PVP_(k90) combinations. Threefactors were varied for each experiment, PVP_(k90) concentration (20-40mg/ml), Compound I concentration (0.3-0.7 mg/ml), and % isopropylalcohol (10-40% by volume IPA). From the experiments it was determinedthat high PVP_(k90) level (40 mg/ml), high Compound I (0.7 mg/ml), andlow % IPA level (10%) was the most favorable formulation for theCompound I/PVP_(k90) combinations.

[0050] A solution of Compound I and PVP was prepared and applied to thesurface of a polyvinylchloride (PVC) intermittent urinary catheter. Thissolution contained 0.7 mg/ml of Compound I and 40 mg/ml of PVP_(k90) ina solvent system of 10% (by volume) isopropyl alcohol and 90% (byvolume) water.

[0051] The surface of the PVC catheter was cleaned by wiping with analcohol soaked cloth. The coating was applied to the catheter by a dipmethod at a speed of 1 cm/s. The coating was illuminated wet to dry witha Dymax lamp (as previously described) for 4 minutes, while the catheterwas rotated.

Durability and Lubricity

[0052] To assess lubricity and tenacity of coated parts, frictionalforce over both the first and last 5 cycles of a 60 cycle test wasevaluated. The coated catheters were evaluated by a horizontal sledstyle friction test method (modified ASTM D-1894, as described below).

[0053] Regenerated cellulose (Spectra/Por molecular porous membrane,MWCO: 6-8,000, flat width 50 mm, part #132665, available from SpectrumMedical Industries, Inc., Los Angeles, Calif.) was hydrated and thenwrapped around a 200 gram stainless steel sled. The sheet of cellulosewas clipped together tightly on the opposite side of the sled. The sledwith rotatable arm was then attached to a 250 gram Chatillon DigitalForce Gauge (DGGHS, 250×0.1) with computer interface. The testingsurface was mounted on a 22.5 inch positioning rail table withmicro-stepper motor control (Compumotor SX6 Indexer/Drive).

[0054] The parts to be tested were hydrated in deionized water andclamped onto the test surface 1 inch (or approximately 2.5 cm) apart.The hydrated cellulose covered sled was placed on top of the parts.Initial force measurements were taken while the sled moved at 0.5 cm/secover a 5 cm section for five push/pull cycles. The sled then continuedcycling over the coated samples 50 push/pull cycles at 5 cm/sec tosimulate abrasion. The velocity was then decreased back to 0.5 cm/secand the final force measurements were taken over another five push/pullcycles.

[0055] As shown in FIG. 1 below, the results show that the CompoundI/PVP_(k90) combination provided a superior lubricious hydrogel matrixin terms of durability. For the Compound I formulation, the grams offorce remained relatively constant for all 60 cycles, indicating adurable coating.

Example 5 Partial Thromboplastin Time of Coating Agents

[0056] An experiment was conducted to determine the hemocompatability ofthe coating agent when attached to a support surface.

[0057] A useful test in determining the hemocompatibility of a reagentis the partial thromboplastin time (PTT) test. The PTT is a test of theintrinsic (factors VIII, IX, XI, and XII) and common (fibrinogen,prothrombin, factors V and X) pathways of coagulation. A mixture ofplasma and phospholipid platelet substitute (rabbit brain cephalin) isrecalcified and the time required for the appearance of fibrin strandsmeasured.

[0058] The PTT was tested to determine whether Compound I or Compound IIhave the ability to extend the control PTT. A test tube of rabbit braincephalin (Sigma #RBC) in 0.85% NaCl and a test tube of 0.02 M CaCl₂ wasbrought to 37° C. in a water bath. Dade Ci-trol coagulation controllyophilized plasma (Dade International, Inc., product no. 34224-10) wasreconstituted in sterile deionized water. In 10×75 mm glass test tubes,100 μl reconstituted plasma and 100 μl RBC were mixed and incubated at37° C. in a water bath for 5 minutes. Next, 50 μl of sample (deionizedwater, a photocrosslinkable polyvinylpyrrolidone (available fromSurModics, Inc., product no. PVO5), or Compound I or II) was added andmixed. While simultaneously starting a stop watch, 100 μl of 0.02 MCaCl₂ was added to initiate the clotting cascade. After 40 seconds hadpassed, the test tubes were shaken lightly, observed for fibrinformation, and the number of seconds was recorded.

[0059] All samples were tested in duplicate. The appropriate controlPTT, depending upon what solvent in which the reagent was dissolved, wassubtracted from the average PTT for the reagent to give the time thecontrol PTT was extended.

[0060] The results of a PTT experiment with two different concentrationsof each reagent are shown in Table 1. The polymer PVO5, which does nothave any sulfonate groups, did not extend the deionized water controlPTT. Compounds I and II, which contain sulfonate groups, were able toconsiderably extend their control PTT's at both concentrations tested.At the higher of the two final concentrations tested, Compound II isable to extend the PTT from its water control by 1 hour or more, andCompound II is able to extend the 50% IPA control PTT by 1 hour. Theseresults show that the reagents were able to inhibit the coagulationcascade, and therefore could be beneficial for hemocompatibleapplications. TABLE 1 PTT of sulfonate reagents. Time Extended BeyondFinal Average Control Concentration Formed PTT PTT Sample (mg/ml)Solvent Clot (seconds) (seconds) DI H₂O — — yes 53 — control 50% IPA — —yes 78 — control PVO5 0.7 H₂O yes 53 0 Compound 0.7 H₂O yes 117 64 ICompound 0.7 50% yes 134 56 II IPA Compound 1.43 H₂O no >3600 >3600 ICompound 1.29 50% yes 3600 3522 II IPA

What is claimed is:
 1. A reagent useful as a surface coating agent, thereagent comprising a nonpolymeric core molecule comprising an aromaticgroup, the core molecule having attached thereto, either directly orindirectly, one or more substituents comprising negatively chargedgroups, and two or more photoreactive species.
 2. The reagent of claim 1wherein the negatively charged groups are independently selected fromsalts of organic acids.
 3. The reagent of claim 2 wherein the organicacids are selected from sulfonic acid, carboxylic acid, and phosphoricacid.
 4. The reagent of claim 1 wherein the cyclic group is a benzeneradical.
 5. The reagent of claim 1 wherein the photoreactive species areindependently aryl ketones.
 6. The reagent of claim 5 wherein each arylketone is independently selected from the group acetophenone,benzophenone, anthraquinone, anthrone, and anthrone-like heterocycles,and their substituted derivatives.
 7. The reagent of claim 1 furthercomprising one or more spacer groups attaching correspondingphotoreactive species to the core molecule.
 8. The reagent of claim 7wherein the spacer groups each independently comprise a radical of theformula: —O—(CH₂)_(n)— wherein n is a whole number equal to at leastone.
 9. The reagent of claim 7 wherein the spacer groups eachindependently comprise a radical of the formula: —(C₂H₄O)_(m)—C₂H₄O—wherein m is a whole number equal to at least one.
 10. The reagent ofclaim 1 wherein the reagent is selected from the group4,5-bis(4-benzoylphenylmethyleneoxy) benzene-1,3-disulfonic aciddi(potassium and/or sodium) salt, 2,5-bis(4-benzoylphenylmethyleneoxy)benzene-1,4-disulfonic acid di(potassium and/or sodium) salt,2,5-bis(4-benzoylphenylmethyleneoxy) benzene-1-sulfonic acidmonopotassium and/or monosodium salt.
 11. The reagent of claim 1 whereinthe reagent is of the formula:

wherein X₁ comprises a first photoreactive species; X₂ comprises asecond photoreactive species; Y comprises a nonpolymeric core moleculecomprising an aromatic group; and Z comprises at least one chargedgroup.
 12. The reagent of claim 11 wherein the Y group comprises benzeneradical.
 13. The reagent of claim 12 wherein the charged groups Z areindependently selected from the organic acids that include sulfonicacid, carboxylic acid, and phosphoric acid.
 14. The reagent of claim 12wherein the photoreactive species of X₁ and X₂ are independently arylketones.
 15. The reagent of claim 14 wherein the aryl ketones areselected from the group acetophenone, benzophenone, anthraquinone,anthrone, and anthrone-like heterocycles, and their substitutedderivatives.